Prep Room
Sign inCreate account
Code Room
Vibe codingHardvc-g154
Subject Ai property testingLevel Senior–Staff~21 minCommon in Algorithms & data structures interviewsIndustries Software development

Question

An AI agent wrote a property-based test (fast-check, TypeScript) for your dedupe(arr) function. The property looks principled:

ts
fc.assert(fc.property(fc.array(fc.integer()), (arr) => {  const expected = [...new Set(arr)];  expect(dedupe(arr)).toEqual(expected);}));

It passes. A teammate says 'great, the property proves dedupe is correct.' What's the subtle problem with using [...new Set(arr)] as the oracle here, and when does this pattern bite?

What a strong answer looks like

Treat the AI’s output as a draft to verify, not an answer to trust. Name the specific flaw and the input that triggers it, say how you’d catch it — tests, edge cases, reading critically — and how you’d re-prompt or decompose to get it right.

Learn the concepts
Describe your solution

Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.

Run or narrate your approach, then ask the coach.